68. Article 4 prescribes
(very simply) three classes of landfill site-for hazardous,[38]
non­hazardous[39]
and inert[40]
waste. Article 6 prescribes that landfill sites designated
for hazardous and inert wastes may respectively be used only for
those categories of waste; non-hazardous sites may, however, be
used for municipal waste as well "non­hazardous waste
of any other origin". Article 5(2) prohibits the use
of landfill for liquid waste; explosive, corrosive, oxidising
and flammable waste; hospital and other clinical waste; and (with
certain exceptions) tyres: we discuss these further below.

69. The rigid scheme
for the separate use of landfills for hazardous, non­hazardous
and inert wastes was challenged by industry witnesses. In particular,
there was consistent criticism of the proposed system of single-purpose
containment sites ("monofills") for hazardous wastes.
Friends of the Earth, however, suggested that if landfill was
seen essentially as a storage mechanism, and if the more hazardous
types of waste were subjected to pre-treatment, such as vitrification,
monofill was preferable to co-disposal (see paragraphs 74
and 83-9) (Q 152).

70. As drafted, the
requirements of Article 6(2) relating to the contents of
hazardous waste sites were thought by some witnesses to be ambiguous-even
to the extent of permitting the practice of co­disposal to
continue. The Commission confirmed to us that this was not the
intention: "hazardous waste landfill" would be for disposal
of hazardous waste only-ie it could not contain biodegradable
materials (Q 286). We find this unsatisfactory: many wastes
which are hazardous according to the Hazardous Waste Directive's
definition are themselves biodegradable (eg dilute phenolic
solutions, oil interceptor contents, or metal salts) in an appropriate
environment. Whilst the more reactive materials will decompose
in a hazardous waste only site, those which require an active
microbial population for their biodegradation are less likely
to do so. This is one of the arguments for co­disposal (see
paragraphs 83-91).

71. The DETR's compliance
cost assessment indicates that some 2.3 million tonnes of difficult[41]
solid wastes are currently co­disposed, of which about 2.2
million tonnes would be diverted to hazardous waste monofills:
disposal of the remaining 0.1 million tonnes would be split
evenly between incineration and solidification prior to landfill.

72. We note that
some hazardous wastes with no leaching qualities (eg asbestos)
pose no environmental threat if entombed and securely protected
from subsequent disturbance. We see no reason why, subject to
the careful controls already in place under UK legislation, such
wastes should not continue to be landfilled with mixed municipal
waste, thereby leaving more capacity in hazardous monofill sites
for disposal of materials which really need to be disposed in
them.

73. The compliance cost
assessment also indicates that between 200,000 and 400,000 tonnes
of clinical and similar waste are generated each year in the UK,
of which 75 per cent is incinerated and the remainder landfilled.
We heard no satisfactory evidence as to how the proportion
of clinical waste currently landfilled should in future be dealt
with, but in our view the right solution for all clinical waste
is hygienic incineration.

74. Industry witnesses
told us that private sector operators in the UK would be unlikely
to provide the hazardous waste only monofills which the change
in disposal policy brought about by the Directive would require.
We share the industry's concern over the proposals to create
a rigid class of hazardous waste monofills, which would provide
nothing more than long­term storage for hazardous waste materials,
with all that that implies for monitoring and future liabilities.
In our view it is essential, if the system is to work at all satisfactorily,
that wastes consigned to hazardous sites should be pre-treated,
eg by vitrification, to minimise their hazardous properties
and, once landfilled, should be the subject of rigid systems of
monitoring: otherwise we would regard the practice as fundamentally
unsustainable. It is true that pre-treatment of all landfilled
waste is a requirement under Article 6, but as we discuss
in paragraphs 80-2, the requirement is broadly drafted and in
this instance a more prescriptive approach may be called for.
It is not clear to us whether additional treatment capacity is
currently available or could be made available in time to meet
the Directive's requirements.

75. Article 5(2)a
would ban liquid waste going to landfill. No definition of "liquid"
is given and witnesses found difficulty with
the proposal, particularly in relation to sludges. The Water Services
Association were particularly concerned about the implications
for sewage sludge (some 10 per cent of which currently
went to landfill) if public opposition to landspreading (see paragraph 25)
were to gain momentum (p 205). The European Parliament has
proposed to remedy the situation by defining liquid waste as fluid
containing up to 45 per cent solids by weight and with flow
characteristics to be determined by the Committee established
under Article 16.

76. Whilst the amendment
proposed by the European Parliament has the merit of providing
a measurable criterion, we are concerned that the proposed percentage
by weight of solids is very high. Many filter cakes, for example,
have a percentage solids content of 30-40 per cent by weight
and no flow characteristics whatsoever. As drafted, the amendment
would (and is evidently intended to) outlaw the landfill disposal
of all sewage sludge, on which the UK depends at present for about
10 per cent of the total amount disposed of in England and
Wales-the remainder being mostly spread on land and therefore
outside the scope of the Directive. We recommend that if landfill
is now longer available, sewage sludge with no recoverable value
should in future be incinerated in a carefully controlled manner.

77. The compliance cost
assessment also indicates that 0.5 million tonnes of difficult
liquid waste is currently thought to be landfilled: it is estimated
that the proposed ban on liquid waste landfill would require 0.4
million tonnes to be pre­treated prior to discharge to sewer,
with the remaining 0.1 million tonnes divided equally between
incineration and solidification prior to landfill.

78. We were told that
the proposed ban on liquid (however defined) waste to landfill
would raise problems for the UK, since landfill site leachate
is defined as a waste under domestic legislation.[42]
It is not entirely clear, however, whether the recirculation of
leachate within the landfill site that produces it would constitute
a waste treatment process and thus require a waste management
licence. Since such recirculation within a landfill effects a
considerable reduction in biodegradable content, this needs urgent
clarification. In our view this would create an absurd situation
for the waste management industry and would undermine the approach
which we recommend for dealing with active and closed landfill
sites during the implementation period for the measures in Article 5.
We therefore recommend that the Directive should expressly permit
the recirculation of leachate within landfill sites for the purposes
of accelerating biodegradation and optimising methane recovery.

79. The Commission's
reasons for proposing a ban on landfilling of used tyres (whole
or shredded) were mentioned in paragraph 27. The European
Parliament has proposed that all types of tyre should be banned
(ie with no exception for bicycle and very large tyres).
It remains unclear to us why, if tyres are to be banned, there
should be any exemptions. It was suggested to us that whole tyres
were useful as drainage blankets for landfills. We are, however,
not convinced that there is a case for continuing with this practice.
As for disposal, we recommend that tyres should, as far as possible,
be shredded and found uses such as being mixed with tarmac for
playground surfacing; otherwise incineration may have to be the
answer.

80. Another significant
provision of Article 6 is that "only waste that has
been subject to treatment is landfilled". Witnesses questioned
whether the definition of "treatment" in Article 2
(see paragraph 26) was adequate; they also questioned why inert
waste, or waste which had itself been the subject of pretreatment,
should under Article 6 be subjected to "treatment".
The Confederation of British Industry (CBI) was concerned that
the definition was over-prescriptive (p 148).

81. Dr Krämer assured
us that the Commission would be adjusting the drafting to clarify
that neither industrial waste that is itself the result of a pre­treatment
nor inert waste will necessarily require treatment before landfill.
The European Parliament has proposed an amendment on similar lines.

82. With the amendments
now proposed by the European Parliament and indicated to us by
the Commission, we are satisfied that the definition of "treatment"
in Article 2 is adequate. We note that the definition would
already cover incineration, which is of course a form of pre­treatment;
we also note that the purpose of the Commission's intentionally
broad definition is to encourage the choice of options higher
up the waste management hierarchy. (See paragraph 26)

85. Whilst the Government's
stance in the Council may be motivated primarily by the need to
secure a political consensus, the evidence in favour of co­disposal
is in fact not entirely clear­cut. According to the Environment
Agency, the United Kingdom has spent some £10 million
on co­disposal research, which has demonstrated the environmental
benefits of the approach. Other evidence reflected a widespread
conviction amongst the industry that co­disposal was a sound
practice which contributed to the chemical transformation and
immobilisation of hazardous materials and substances co­disposed
with biodegradable waste. Whilst specific detail was not forthcoming,
we found that the industry's evidence pointed to a number of beneficial
effects of co­disposal.

86. The evidence left
us with some uncertainty about the status of the "flushing
bioreactor" concept-an approach based on providing controlled
conditions in which leachate is mechanically recirculated through
landfill waste so that it breaks down more rapidly and evenly.
The DETR's most recent guidance on landfill operation (DOE Waste
Management Paper 26B)[44]
is concerned with encouraging this mode of operation, and the
EA told us that it was regulating landfills in a way which would
encourage their operation as flushing bioreactors. The Commission,
however, clearly believed that the flushing bioreactor was merely
a concept-Dr Krämer told the Sub-Committee that he did not
believe that one existed. Recirculation of leachate is, in fact,
standard practice in modern UK landfill sites: the Sub-Committee
visited an example of such a site in Fife, where the site leachate
is routinely recirculated by irrigation beneath the surface cap.

87. Whether or not the
flushing bioreactor can be said to exist, what is not in dispute
is that the ban on co-disposal would ipso facto rule it
out for the future, since under UK law (as we have already noted)
landfill leachate is defined as a liquid waste and would therefore
be banned from recirculation by the Directive, unless our recommendation
in paragraph 78 is accepted.

88. Whilst the position
previously reached, and likely to be reached again, by the Council
of Ministers could be explained in terms of political expediency
rather than rational argument, it is legitimate to apply the precautionary
principle[45]
here. All landfill sites, including those designed to be "containment"
sites, have the potential to fail and cause damage to the environment.
They raise problems with long­term monitoring and the question
of ultimate responsibility.

89. Nevertheless, co­disposal
is itself a form of treatment in situ. We recognise the
widespread view of the UK industry that the process of co­disposal,
by assisting (and in the case of the bioreactor accelerating)
decomposition and by neutralising certain hazardous components
of waste, is environmentally beneficial. We also note that research
by the Department of the Environment and the Environment Agency
has supported these claims. We believe that to replace the
co­disposal of industrial and biodegradable wastes with a
rigid system of segregation and monodisposal of hazardous industrial
wastes is to fail to recognise that judicious and carefully regulated
mixing of certain low-hazard industrial wastes (eg organics)
with biodegradable municipal waste (which can itself contain a
range of hazardous materials) is unlikely to produce an end result
materially different from that of a purely municipal landfill.

90. We recognise
that the management and aftercare of sites currently operated
on flushing bioreactor principles will have to be approached with
care. On the basis of the available evidence, we are doubtful
whether the processes within a flushing bioreactor are capable
of precise specification or their effects measurable with any
certainty. The principle, however, of recirculation of leachate
and otherwise maintaining optimum conditions for progressive decomposition,
coupled with collection and use of landfill gas, within existing
mixed waste sites should, in our view, be supported. We note that
the Royal Commission on Environmental Pollution in 1996 recommended
that the Department of the Environment and the waste disposal
industry should consider how the flushing bioreactor approach
could be made financially attractive both then and after co­disposal
of industrial wastes ceased.[46]
This recommendation, in our view, remains valid for the management
of existing co­disposal sites, even if no new ones are constructed
during the implementation period for Article 5 of the Directive,
and should continue to be the subject of research.

91. We recommend
that one of the principal management aims of all sites which currently
take (or have until recently taken) significant quantities of
industrial and biodegradable waste should be to optimise methane
recovery for as long as the process remains viable. Such a measure
would be consistent with the Commission's communication on methane
reduction and would help to reduce the timescale within which
such sites pose a threat to the environment.